Textbook Question
Predict the products of the following reactions:
(g)
21. Aldehydes and Ketones: Nucleophilic Addition
Imine vs Enamine
8:43 minutesProblem 8b
Textbook Question
Give the expected products of the following acid-catalyzed reactions.
(b) acetophenone + dimethylamine
Verified step by step guidance1
Identify the type of reaction: This is an acid-catalyzed reaction between acetophenone (a ketone) and dimethylamine (a secondary amine). Such reactions typically lead to the formation of an imine or an enamine, depending on the conditions.
Understand the mechanism: In the presence of an acid catalyst, the carbonyl group of acetophenone (C=O) becomes protonated, increasing its electrophilicity. This makes the carbonyl carbon more susceptible to nucleophilic attack by dimethylamine.
Describe the nucleophilic attack: The lone pair of electrons on the nitrogen atom of dimethylamine attacks the carbonyl carbon of acetophenone, forming a tetrahedral intermediate.
Explain the dehydration step: After the tetrahedral intermediate forms, a proton transfer occurs, followed by the elimination of water (H2O). This step is facilitated by the acid catalyst and leads to the formation of an imine or enamine product.
Determine the final product: Since dimethylamine is a secondary amine, the reaction will likely result in the formation of an enamine. The enamine structure will have a C=C bond adjacent to the nitrogen atom of dimethylamine.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Catalyzed Reactions
Acid-catalyzed reactions involve the use of an acid to increase the rate of a chemical reaction. In organic chemistry, acids can protonate reactants, making them more electrophilic and facilitating nucleophilic attacks. This is particularly important in reactions involving carbonyl compounds, where the carbonyl carbon becomes more reactive in the presence of an acid.
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Nucleophilic Addition to Carbonyls
Nucleophilic addition to carbonyls is a fundamental reaction in organic chemistry where a nucleophile attacks the electrophilic carbon of a carbonyl group (C=O). In the case of acetophenone, the carbonyl carbon is susceptible to attack by nucleophiles like dimethylamine, leading to the formation of an intermediate that can undergo further transformations, such as protonation or dehydration.
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Formation of Imines
The formation of imines is a key reaction where a primary amine reacts with a carbonyl compound, resulting in the formation of an imine (C=N) after the elimination of water. In the context of acetophenone and dimethylamine, the reaction will yield an imine product, which is characterized by a double bond between carbon and nitrogen, and is often formed under acidic conditions that facilitate the dehydration step.
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